The present invention relates to a propulsion-control system for a motor vehicle provided with:
an internal combustion engine,
a transmission system comprising a transmission with discrete ratios, provided with actuator means for engaging/disengaging the ratios,
a reversible electric machine which includes a rotor and a stator, is interposed between the internal combustion engine and the transmission system and is suitable for operating selectively as a generator and as an electric motor,
a first clutch and a second clutch which can be operated selectively to control the connection of the rotor of the electric machine to the transmission system and to the internal combustion engine, respectively,
sensor means arranged for supplying electrical signals indicative of operating conditions of the vehicle, of the internal combustion engine, and of the electric machine, and
control means for controlling the internal combustion engine, the electric machine, the first and second clutches, and the actuator means for engaging/disengaging the ratios, in accordance with predetermined procedures in dependence on the signals provided by the sensor means,
the control means being arranged, in particular, to implement a stop-start function in which, during a stop stage, upon the occurrence of first predetermined operating conditions of the vehicle, the internal combustion engine is disconnected from the electric machine and from the transmission system and is switched off and then, in a subsequent start stage, upon the occurrence of second predetermined operating conditions of the vehicle, is automatically restarted by means of the electric machine, operating as a motor, and is then reconnected to the transmission system.
A hybrid motor-vehicle propulsion system known from prior international patent application PCT/EP98/06922 includes an internal combustion engine, a reversible electric machine, a transmission system comprising a transmission with discrete ratios, as well as a first clutch and a second clutch which can be operated selectively to control the connection of the rotor of the electric machine to the transmission system and to the internal combustion engine, respectively. This propulsion system enables a stop-start (or “stop-and-go”) function to be implemented, in which, during the stop stage, the clutch between the internal combustion engine and the electric machine is disengaged whilst the clutch between the electric machine and the transmission system remains engaged, and the internal combustion engine is switched off. During the subsequent start stage, both of the above-mentioned clutches are disengaged and the electric machine is operated as an electric motor. As soon as the speed of rotation of the electric machine exceeds a predetermined threshold value, the clutch between the internal combustion engine and the rotor of the electric machine is engaged in order to start the internal combustion engine. As soon as this has occurred, the clutch between the rotor of the electric machine and the transmission system is engaged so that the vehicle is propelled by the internal combustion engine.